The present invention relates to a glass panel, and more particularly to a glass panel including a plurality of glass sheets, a plurality of spacers interposed between opposed faces of the glass sheets for forming a space therebetween, and a sealing material disposed along the peripheries of the opposed faces for maintaining the space under a gas-tight condition and binding the glass sheets together. The invention relates also to a method of manufacturing such glass panel as well as the spacer to be used therein for maintaining the opposed faces at a predetermined distance therebetween.
With the conventional glass panel of the above-noted type, for the purpose of improvement of heat insulating performance, it is extremely advantageous that the space be evacuated for restricting the heat transfer rate. However, as the inside of the space is evacuated, it becomes necessary for the two glass sheets to be able to endure the external pressure applied thereto.
Incidentally, if the inside of the space is evacuated to about 0.1 atm., the external pressure applied to the outer faces of the glass sheets due to the atmospheric pressure can reach as high as 10 tons/m2 approximately. In order to endure such external pressure, spacers need to be disposed along the opposing faces of the glass sheets.
Conventionally, the above-described glass panel, as shown in FIG. 60 and FIG. 61, employs flat-plate like or column-like spacers 3, which are simply bound between the opposing face 2 of the first glass sheet 1A and the opposing face of the second glass sheet 1B. And, in the manufacture of this glass panel P, the respective spacers 3 are disposed with a predetermined distance therebetween on the opposing face 2 of the first glass sheet 1A and the opposing face 2 of the other second glass sheet 1B is disposed in contact with the spacer 3, and then a sealing material 6 made of low melting glass is sealed by melting on a peripheral edge 1a. 
However, with the conventional glass panel described above, since the entire end faces of the spacer 3 are placed in contact with the opposing faces 2 of the glass sheets 1, heat conduction can occur through the spacer 3 in spite of the evacuation of the inside of the space C, leading to deterioration of heat insulating performance of the glass panel P. In order to reduce such heat conduction through the spacer 3, its heat conducting cross sectional area may be reduced. Yet, if the contact face of the spacer 3 for contacting the glass sheet 1 is minimized in order to reduce its heat conducting cross sectional area, such contact face may result in stress concentration to the glass sheet 1, so that hertzian crack due to external pressure is apt to occur.
Further, if the spacer 3 is formed thin in order to reduce its heat conducting cross sectional area, the spacer 3 may be broken by an external bending force when the glass panel P is warped due to a difference in the heat expansion rates of the two glass sheets 1 because of the temperature difference between the outside and the inside of the glass panel P.
Then, an object of the present invention is to provide a glass panel which can restrict heat conduction via the spacer 3 while effectively protecting the glass sheets 1 against development of crack in the glass sheets such as the hertzian crack and which can also prevent damage of the spacer 3 and also to provide a spacer for use in such glass panel.
According to a glass panel relating to claim 1, as shown in FIG. 1, a plurality of spacers 3 are disposed in a space C formed between and along e.g. a first opposing face 2A of a first glass sheet 1A and a second opposing face 2B of a second glass sheet 1B. The spacer 3 includes, in one side 3a thereof, a plurality of projections and recesses. The projections 4 of these projections and recesses are formed to have a predetermined height from the other side 3b, so that these form a contact portion 5 capable of coming into contact with the first opposing face 2A. And, this contact portion 5 is movable relative to the first opposing face 2A.
In this construction, the plurality of projections 4 are formed on the one side 3a of the spacer 3 so as to form the contact portion 5 for coming into contact with the glass sheet 1. Thus, the spacer 3 may come into contact with a greater area of the glass sheet 1. Hence, it becomes possible to prevent stress concentration at the portion of the glass sheet 1 contacting the contact portion 5, thus preventing development of crack such as the hertzian crack in the glass sheet 1.
Further, as the heights of the projections 4 for contacting the glass sheet 1 are set at a predetermined constant height from the other side 3b, all of the projections 4 come into contact with the glass sheet 1, thus assuring a large contact area to the glass sheet 1. On the other hand, as it is possible to prevent the entire surface of the one side 3a of the spacer from coming into contact with the glass sheet 1, the heat resistance may be increased.
Also, since the contact portion 5 of the spacer 3 is movable relative to the opposing face 2, even if there is developed a warp in the glass panel P, the resultant displacement between the spacer 3 and the glass sheet 1 along the direction of its surface may be offset by such relative movement, thereby to prevent development of associated shearing force within the glass sheet 1 or the spacer 3, so that damage of the glass sheet and the spacer 3 may be avoided.
A glass panel relating to claim 2 is characterized in that the projections are formed by means of cutting.
With this construction, in addition to the effect achieved by the glass panel of claim 1 described above, there is obtained a further effect of facilitation of the manufacture of the spacer 3.
That is to say, if the projections forming the contact portion 5 are formed by means of cutting, the cutting operation per se is simple and easy and the adjustment of the height of the projections from the other side too is easy. For instance, the side face to be cut will be formed in advance as a flat face adjusted to the predetermined height from the other side and then grooves will be formed by cutting, whereby the projections and recesses are formed. Accordingly, the projections may be formed to the predetermined height.
A glass panel relating to claim 3, as shown in FIG. 1, is characterized in that the other side 3b of the spacer 3 is fixedly formed on the second opposing face 2B.
With this construction, in addition to the effect achieved by the glass panel of claim 1 or 2, there are obtained further advantages that the assembly of the glass panel may be facilitated and that the spacer 3 will hardly be displaced inside the space C during use.
That is to say, with this construction, by fixedly forming the other side 3b of the spacer 3 on the second opposing face 2B, it is possible to effectively prevent tumbling or rolling of the spacer 3. Moreover, as the spacer 3 need not be maintained in position especially, as shown in FIG. 9 for instance, the second glass sheet 1B may be superposed with a desired posture over the first glass sheet 1A. Further, when the glass sheets 1 are flexed due to e.g. wind pressure so as to relax the distance between the two glass sheets 1A, 1B, there will occur no dislocation of the spacer 3 inside the space C.
A glass panel relating to claim 4, as shown in FIG. 1, is characterized in that the other side 3b of the spacer 3 is bonded to the second opposing face 2B.
With this construction, the effect of the construction of claim 3 described above may be obtained more reliably. That is to say, by bonding the other side 3b of the spacer 3 to the second glass sheet 1B, the fixation of the spacer 3 may be surer. For instance, as shown in FIG. 9 and FIG. 10, after the spacer 3 is fixed, the second glass sheet 1B will be superposed on the first glass sheet 1A with the spacer 3 being oriented downward. In this way, the second glass sheet 1B may be handled with any desired posture. As in FIG. 9, the second glass sheet 1B with its opposing face 2B oriented downward may be assembled with the first glass sheet 1A.
According to a glass panel relating to claim 5, the spacer 5 may be made of low melting glass.
With this construction, in addition to the effects achieved by the glass panels of claims 1 through 4, there is obtained another advantage that the manufacture and arrangement of the spacers 3 are facilitated.
Namely, for example, the low melting glass will be set on the second glass sheet 1B and then this is heated so as to form the spacer 3. For instance, frit of the low melting glass will be made into paste and then this is printed on the second opposing face 2B of the second glass sheet 1B and then baked, whereby a pre-spacer forming member 30 may be fixedly set on the second opposing face 2B. Then, by pressing this pre-spacer forming member 30 against the other glass sheet into a predetermined height at a temperature lower than the melting point, the spacer 3 may be formed with the predetermined height precisely.
In the course of formation of this pre-spacer forming member 30, even if the paste is heated and baked, by setting the melting point of the second glass sheet 1B higher than this temperature, the second glass sheet 1B will not be affected by the pressing or not be damaged by the heat.
According to a glass panel relating to claim 6, the spacer 3 may be made of crystalline glass.
With this construction, in addition to the effect achieved by the glass panel of claim 5, there is obtained a further advantage that the spacer 3 may be reinforced although it is baked at the low temperature.
That is to say, for instance, frit of low-melting crystalline glass will be prepared into paste and the pre-spacer forming member 30 will be shaped at a temperature higher than the melting temperature into predetermined dimensions and shape, and then cooled under predetermined cooling conditions, whereby the spacer 3 may be formed of the crystalline glass. As a result, the strength of the spacer 3 is increased and its melting point is raised. Hence, when the peripheral edge of the glass panel P is sealed with low melting glass for instance, the spacer 3 will not be softened. And, the peripheral edge may be sealed with low-melting glass of similar properties, so that the manufacturing process of the glass panel may be simplified.
According to a glass panel relating to claim 7, the sealing material 6 may be comprised of low-melting glass having a lower softening point than the low melting glass forming the spacer 3.
With this construction, in addition to the effect achieved by the glass panel of claim 5 or 6, there is obtained a further advantage that the spacer 3 may be protected in the course of assembly of the glass panel P.
That is to say, when the peripheral edge 1a of the glass panel P is sealed with the sealing material 6 comprised of the low melting glass, even if the sealing material 6 is heated above the softening temperature, it is possible to prevent softening of the spacer 3 disposed in advance. As a result, it is possible to prevent such inconvenience as deformation of the spacer 3.
According to a glass panel relating to claim 8, as shown in FIG. 22, in a glass panel in which a pair of glass sheets 1A, 1B are disposed with a predetermined distance therebetween to form a space C and an outer peripheral sealing portion is provided along the entire peripheral edges of the two glass sheets 1A, 1B so as to seal the space C under evacuated condition, a spacer 3 is interposed between a first opposing face 2A of the first glass sheet 1A and a second opposing face 1B of the second glass sheet 1B for maintaining the opposing faces 2A, 2B with a predetermined distance therebetween. This spacer 3 includes a pair of contact portions 5 for coming into contact with the two opposing faces 2A, 2B respectively and a heat-transfer resisting portion formed between the pair of contact portions 5, 5, the heat-transfer resisting portion having a smaller cross sectional area than a contacting area between each contact portion 5 and the glass sheet 1.
With this construction, the heat-transfer resisting portion 20 is formed between the pair of contact portions 5, 5.
More particularly, with reference to an example shown in FIG. 22, there are provided a contact portion 5 provided by a flat plate portion 21 for coming into contact with the opposing face 2A of the first glass sheet 1A and the other contact portion 5, and this other contact portion 5 is provided by forming, into a flat surface, a bottom 22a of a base portion 22 for coming into contact with the opposing face 2B of the second glass sheet 1B. And, the base portion 22 includes, upwardly of the bottom 22a, an outer face 22b which is formed as a revolving surface. And, between the top of the base portion 22 and the back of the contact portion 5 are connected together to form a border portion 23. This border portion 23 has a reduced cross sectional area forming a constricted passage for heat transfer; hence, this border portion 23 provides the heat-transfer resisting portion 20.
Further, with this construction, the contact portions 5 for coming into contact with the two glass sheets 1A, 1B may be maintained at a contact area sufficient for preventing damage of the glass and damage of the glass sheets may be prevented. That is, in this construction, between the two contact portions 5, 5, there is formed the heat-transfer resisting portion 20 having a smaller cross sectional area than the contact area between the contact portion 5 and the glass sheet 1. In this regard, generally, heat-transfer resistance is in inverse portion to the cross sectional area. Then, regardless of the magnitude of the contact area between the contact portion 5 and the opposing faces 2A, 2B, the heat conduction between the opposing faces 2A, 2B via the spacer 3 may be small. As described above, according to the glass panel having this construction, hertzian crack may be prevented and also the external pressure applied to the glass sheets 1 through contact with the spacer 3 may be reduced, whereby damage of the glass plates 1 may be prevented.
According to a glass panel relating to claim 9, as shown in FIG. 23, opposed contact portions 5, 5 of the spacer 3 are provided in the form of plate-like portions 24 and between these plate-like portions 24, 24, there is formed a column-like portion 25 having a smaller cross sectional area than the contact area between the plate-like portion 24 and the glass sheet 1, so that this column-like portion 25 provides a heat-transfer resisting portion 20.
With this construction, the contact portions 5 are provided in the form of the plate-like portions 24 which come into face contact with the respective opposing faces 2A, 2B of the two glass sheets 1A, 1B, so that stress concentration to the two glass sheets 1A, 1B may be relieved. Moreover, between the plate-like portions 24, 24 which come into contact with the opposing faces 2A, 2B, there is formed the column-like portion 25 having a smaller cross sectional area than their contact area, so that heat conduction via the spacer 3 may be restricted by the column-like portion 25.
In this manner, if the spacer 3 having the above construction is employed, the heat-transfer resistance of the spacer 3 may be enhanced, while the contact area between the spacer 3 and the opposing face 2A, 2B may be maintained at a required magnitude.
According to a glass panel relating to claim 10, a truncated conical base portion 22 integrally forms a plate-like portion 21 having a greater area than the top surface of the base portion 22, and a border portion 23 between the base portion 22 and the plate-like portion 21 is provided as the heat-transfer resisting portion 20, and the contact portions 5 are provided in the plate-like portion 21 and a bottom 22a of the base portion 22.
That is to say, as shown in FIG. 24, the plate-like portion 21 having a greater area than the top face of the base portion 22 is formed integrally on the truncated conical base portion 22, and the border portion 23 between the base portion 22 and the plate-like portion 21 is formed as the heat-transfer resisting portion 20.
With this construction, the contact portion 5 for contacting the opposing face 2A of the first glass sheet 1A is provided by the plate-like portion 21 and the contact portion 5 for contacting the opposing face 2B of the second glass sheet 1B is provided by the bottom 22a of the truncated conical base portion 22 formed integral with the plate-like portion 21. So that, the large contact areas for contacting the two opposed faces 2A, 2B are maintained, and at the same time the heat-transfer resisting portion 20 is provided by the reduced-diameter top of the base portion 22, i.e. the border portion 23 between base portion 22 and the plate-like portion 21, whereby the heat transfer resistance may be enhanced as well.
According to a glass panel relating to claim 11, as shown in FIG. 25 and FIG. 26, a peripheral wall 26 of a column-like member 25 as the spacer 3 is recessed along its entire periphery so as to form a recessed face portion 27 having a reduced cross section, so that this recessed face portion 27 functions as the heat-transfer resisting portion 20.
If the recessed face portion 27 is defined in the peripheral wall 26 of the spacer 3 like the present construction, the small cross section portion is formed in the middle of the column-like member 25 and the opposed ends thereof provide the contact portions 5. Then, in the middle portion, there is formed the portion having a smaller cross section than the contacting areas, and this portion constitutes the heat-transfer resisting portion 20. Then, the contact area between the opposed glass sheets 1A, 1B and their opposing faces 2A, 2B may be maintained large so as to prevent damage of the glass sheets and at the same time the heat-transfer resisting portion 20 having a smaller cross section is provided for improving the heat insulating performance of the glass panel.
According to a glass panel relating to claim 12, the spacer includes a first contact portion 5a for contacting the first glass sheet 1A, a second contact portion 5b for contacting the second glass sheet 1B, and a through hole 30 in the form of a hole or the like extending from the first contact portion 5a to the second contact portion 5b. 
With the conventional glass panel P, when its transparency as a window pane is considered, as the spacers are densely disposed, the individual spacers tend to show conspicuously when viewed through the glass panel P. And, this tendency is more pronounced when the viewer is located close to the glass panel P.
If the through portion 30 extending from the first contact portion 5a to the second contact portion 5b is formed like the present construction, the spacer 3 blocks a smaller area of the glass surfaces when the glass panel P is seen through, so that the transparency of the glass panel P may be improved.
According to a glass panel relating to claim 13, the spacer is constructed such that the first contact portion 5a and the first glass sheet 1A and also the second contact portion 5b and the second glass sheet 1B respectively come into point or line contact with each other.
If the contact area of the spacer 3 relative to the first glass sheet 1A and also to the second glass sheet 1B is reduced, the heat conduction between the first glass sheet 1A and the second glass sheet 1B may be minimized, so that a glass panel P having superior heat insulating performance may be obtained. Incidentally, with this construction too, the transparency of the spacer 3 achieved in claim 12 may be maintained well.
According to a glass panel relating to claim 8, as shown in FIG. 43 and FIG. 44, a plurality of spacers 3 are interposed between a first opposing face 2A of a first glass sheet 1A and a second opposing face 2B of a second glass sheet 1B so as to form a space C between the first opposing face 2A and the second opposing face 2B, and a sealing material 6 is disposed at peripheral edges of the first and second opposing faces 2A, 2B, the sealing material being capable of maintaining the space C air-tight at the peripheral edges 1a of the glass sheets 1A, 1B and also of bonding the glass sheets 1A, 1B together.
Then, one side of each of the plurality of spacers 3 is bonded to the second opposing face 2B and the other side of each spacer 3 has a smaller diameter than the one side and a predetermined constant height from the one side so as to provide a contact portion 5 capable of coming into contact with the first opposing face 2A, and said contact portion 5 is movable relative to the first opposing face 2A.
With this construction, the spacer 3 is bonded to the second glass sheet 1B. Hence, the spacer 3 does not move or tumble relative to the second glass sheet 1B. Hence, the superposing operation of the glass sheets 1 may be significantly facilitated.
Further, as the spacer has one end formed thick and the other end formed thin, the heat conduction between the contact portion 5 of this spacer 3 and the first glass sheet 1A may be restricted and also the spacer obtains resistance against bending deformation.
Moreover, as the contact portion 5 of the spacer 3 and the first glass sheet 1A are slidable relative to each other, there will occur no shearing warp in the glass sheets in association with flexion of the glass panel P, so that the risk of breakage of the glass sheets too may be eliminated.
As described above, according to the glass panel having this construction, the assembly of the glass panel P is easy. Also, the strength of the spacer 3 per se may be retained while the heat conduction between the first glass sheet 1A and the second glass sheet 1B may be restricted maximally. And, at the same time, the breakage of the glass panel may be prevented.
According to a glass panel relating to claim 9, as shown in FIG. 37, the spacer 3 has a truncated conical shape. Specifically, the spacer 3 is provided in the form of a truncated cone having a base face bonded to the second opposing face 2B and a top face which forms a contact portion 5 capable of coming into contact with the first opposing face 2A.
With this construction, in addition to the effect achieved by the glass panel of claim 8 described above, even when a relative displacement occurs between the first opposing face 1A and the second opposing face 2B along these faces, the internal stress inside the spacer 3 due to an associated bending moment affecting the spacer 3 may be equated, hence, even if the top face of the truncated cone is formed small, breakage of the spacer 3 may be avoided.
According to a method of manufacturing a glass panel relating to claim 10, as illustrated in FIG. 36 and FIGS. 38-44, the method comprises the steps of: disposing a plurality of spacers 3 between a first opposing face 2A of a first glass sheet 1A and a second opposing face 2B of a second glass sheet 1B to form a space C between the first glass sheet 1A and the second glass sheet 1B and sealing and integrating peripheral edges 1a of the first glass sheet 1A and the second glass sheet 1B;
wherein the method comprises the steps of: preparing a paste 7 capable of forming each spacer 3; forming the paste 7 into a predetermined shape having a gradually reduced diameter toward its top and disposing it on the second opposing face 2B; subjecting each paste 7 to a predetermined solidifying operation to provide a plurality of pre-spacer forming members 30; adjusting a contact portion 5 capable of contacting the first glass sheet 1A of each of the plurality of pre-spacer forming members 30 after the solidifying operation thereof into a predetermined height relative to the second opposing face 2B so as to provide the spacers 3; and integrating the first glass sheet 1A and the second glass sheet 1B together with placing the first opposing face 2A in opposition to the height-adjusted contact portion 5.
With this method, as the paste 7 is disposed at a predetermined position on the second opposing face 2B and then solidified, the formed spacers 3 are disposed at the predetermined positions on the second glass sheet 1B and have one end thereof bonded to the second opposing face 2B. And, as the contact portion 5 for coming into contact with the first opposing face 2A ha a smaller diameter than the one side, the contact area relative to the first opposing face 2A may be small, so that the heat-transfer resistance between the first glass sheet 1A and the second glass sheet 1B may be increased. Further, as the one side is formed with a greater diameter than the contact portion 5, deformation in the course of height-adjusting shaping of the pre-spacer forming member 30 may be avoided, so that the spacer 3 may be shaped stably.
For instance, according to this manufacturing method, if the pre-spacer forming member 30 which was disposed at a predetermined position and then subjected to the solidifying operation for heating up to a predetermined baking temperature is shaped for its height adjustment by means of a shaping roll or the like before it is completely solidified in the subsequent cooling operation, a spacer 3 having a predetermined height may be easily obtained.
Further, as the one side is bonded to the second opposing face 2B, the posture of the second glass sheet 1B during the manufacture of the glass panel may be freely selected. Hence, when the two glass sheets 1A, 1B are superposed one on the other, the operations for maintaining the position of the spacer 3 and maintaining the posture of the second glass sheet 1B may be eliminated, whereby the operational efficiency may be improved.
Furthermore, since the contact portion 5 is slidable relative to the first opposing face 2A, as for possible deformation of the glass panel P, associated relative displacement between the first glass sheet 1A and the spacer 3 is permitted, thereby to avoid breakage of these.
According to a method of manufacturing a glass panel relating to claim 11, as shown in FIGS. 36 and 43, FIG. 44 and FIGS. 47 through 52, the method comprises the steps of: interposing a plurality of spacers 3 between a first opposing face 2A of a first glass sheet 1A and a second opposing face 2B of a second glass sheet 1B so as to form a space C between the first glass sheet 1A and the second glass sheet 1B; and sealing and integrating peripheral edges of the first glass sheet 1A and the second glass sheet 1B;
wherein the method comprises the steps of: preparing a paste 7 capable of forming the spacer 3; forming the paste 7 into a predetermined shape having a gradually reduced diameter toward its top and disposing it on the second opposing face 2B; subjecting each paste 7 to a predetermined semi-solidifying operation to provide a plurality of semi-solidified pre-spacer forming members 30; adjusting a contact portion 5 capable of contacting the first glass sheet 1A of each of the plurality of semi-solidified pre-spacer forming members 30 after the semi-solidifying operation thereof into a predetermined height relative to the second opposing face 2B; subjecting the height-adjusted pre-spacer forming members 30 to a predetermined solidifying operation so as to provide a plurality of spacers 3; and integrating the first glass sheet 1A and the second glass sheet 1B together with placing the first opposing face 2A in opposition to the height-adjusted contact portion 5.
With this manufacturing method, as the one side is formed with a greater diameter than the contact portion 5, shape deformation of the pre-spacer forming member 30 during its height-adjusting shaping operation may be avoided, so that the spacer 3 may be formed stably. As the smaller diameter of the contact portion 5 than the one side also serves to reduce the contact area relative to the first opposing face 2A, thereby to increase the heat-transfer resistance between the first glass sheet 1A and the second glass sheet 1B.
Further, as the one side of the spacer 3 is bonded to the second opposing face 2B, the posture of the second glass sheet 1B during the manufacture of the glass panel may be selected freely. So, when the second glass sheet 1B is superposed, the trouble of maintaining the posture of the spacer 3 may be eliminated, so that the operational efficiency may be significantly improved
Moreover, as the contact portion 5 is slidable relative to the first opposing face 2A, even if surface deformation occurs in the glass panel P, the first glass sheet 1A and the spacer 3 may move relative to each other, so that no excessive stress is applied to the spacer 3 and breakage or the like of the spacer 3 may be avoided.
As described above, this manufacturing method provides facilitated assembly of the glass panel and high productivity and provides a glass panel P having improved heat insulating performance.
According to a manufacturing method of a glass panel P relating to claim 12 and 13, as shown in FIG. 37, the spacer 3 of claim 10 and 11 is shaped in the form of a truncated cone.
For instance, the truncated cone may comprise a bottom face thereof as the one side of the spacer 3 bonded to the second opposing face 2B of the second glass sheet 1B and a top face thereof as the contact portion 5 formed on the side of the first opposing face 2A.
With this method, in addition to the effects achieved by the manufacturing methods of claim 10 and 11 there are achieved following effects when the firs glass sheet 1A and the second glass sheet 1B are displaced relative to each other along the faces of the glass sheets. Namely, when the first glass sheet 1A and the second glass sheet 1B are displaced relative to each other, a bending moment will be applied to the spacer 3. However, as this bending moment is smaller on the side of the contact portion 5, then, although the construction is tapered on the side of the contact portion 5, the bending stress within the spacer 3 may be even, so that breakage of the spacer 3 may be effectively prevented even though the top face of the truncated cone is formed small.